Electric wave signaling



Aug. 4, 1936. A. cs, COOLEY ELECTRIC WAVE SIGNALING Filed Dec. 29, 1951 2 Sheets-Sheet 1 .Z/VJdJ/Z) Jury Aug. 4, 1936. A. G. COOLEY 2,049,424

ELECTRIC WAVE SIGNALING Filed Dec. 29, 1951 2 Sheets-Sheet 2 (aw/em balm/ (aez/ z Mm:

Patented Aug. 4, 1936 attain 16 Claims.

It is a well known expedient in the art of electric wave signaling, as for example radio telephony, to combine two oscillations, one of constant high frequency, commonly called carrier wave, and one of much lower frequency which represents the signals to be transmitted. and is usually referred to as modulating wave. The resulting wave, with the modulating wave impressed upon the carrier wave, is referred to as the modulated carrier wave, and can be resolved into a wave of a frequency equal to the sum of the two component frequencies, a second wave of a frequency equal to the difference of these two component frequencies, and a wave of the frequency of the stronger of the two waves. Consequently, if the frequency of the modulating wave varies (as for example in telephony where it conforms to the frequencies comprised in the acoustic oscillations to be transmitted) the modulated carrier covers a frequency range of at least twice the highest modulating frequency, which accounts for example for the well known difficulty of allotting a sufiicient number of transmitting channels for purposes of radio broadcasting.

It is the primary object of the present invention to provide a method, and means for carrying out that method, of impressing signal waves upon a carrier wave substantially without introducing powerful accompanying frequencies or so-called side bands, so that only a narrow transmission channel is required. Other objects will be apparent from the following description of the underlying principle and of several concrete embodiments of the invention by way of explaining its genus, the description referring to drawings, in which Fig. 1 is a diagram of carrier wave, signal wave and the combination thereof obtained according to the present invention;

Fig. 2 shows somewhat enlarged a portion of Fig. 1;

Fig. 3 is a circuit connection diagram of one embodiment of the present invention;

Fig. l'shows a grid voltage-plate current diagram of an electron discharge device as used in.

the present invention; and

Fig. 5 is a circuit diagram of another embodiment of the inventiorn 7 Whereas the previously known modulated carrier wave is produced by continually combining the modulating and carrying waves, the carrieraccording to the present invention (which will herein be referred to as signaled carrier in order to distinguish it from the modulated carrier of the prior art), is produced by regulating the amplitudes of successive cycles of a sinusoidal carrier wave in accordance with the configuration of the modulating wave, whereby the amplitudes are set and regulated only at certain predetermined points during comparatively short adjustable periods of certain cycles of the carrier wave. If adjoining cycles are to have different amplitudes, the change takes place. within a cer tain transient period section, each. cycle otherwise retaining its sinusoidal shape, although the amplitudes'differ. In this manner, the frequency and sinusoidal shape of the signaled carrier are retained over the major portion of the cycle, the signals beingtransmitted substantially only by varying the amplitude of the signaled carrier wave of constant frequency. Only the carrier frequency need be transmitted, since the frequencies which are introduced by the transient period sections are unnecessary for reception and may therefore be filtered out. Besides that, they are of such low power that they can in many cases be ignored.

This new way of impressing signal waves upon a carrier wave is illustrated in Figs. 1 and 2, where C is the sinusoidal carrier wave of constant frequency, M the modulating signal wave and S the signaled wave. Each cycle of S is sinusoidal from B to E, whereas theamplitudes of consecutive cycles vary in accordance with the momen tary value of the signal wave at the beginning of each carrier cycle, if B to E is called a signaled' carrier cycler Thus, presuming that each sinusoidal period section starts at the apex of a cycle, if a certain signaled cycle has during that sinusoidal section an amplitude a at B, and the signal wave increases during that cycle .from b to ZH-n, the next transient section E B brings the amplitude of the signaled carrier to a-i-m, m corresponding to the increase n of the signal wave. 'In this manner, every cycle is during the 40 transient period section adjusted to the momentary value of the signal wave at that time, whereas no change takes place during the section B E which is very much longer and during which the signaled wave, uninfiuenced by the signal wave, l5 retains its sinusoidal shape with the amplitude acquired during the last transient section.

Referring to Fig. 3, an arrangement for carrying out this new method of modulating a. carrier wave will be described. A carrier frequency generator 5 with rotor 2 and armature winding 3 supplies a carrier Wave to a transformer 5 with primaryfi and secondary'l. One terminal of secondary l is connected through a high resistance 8, to the grid iii of an electron discharge device .55

I II. The other side of the secondary I is connected to the filament I4 through an adjustable biasing battery I'I. Another battery I9 is in the output circuit of the electron discharge tube I0. Secondary I and resistance 8 are shunted by a condenser 2I. Incoming signal waves are supplied, for example, through a transformer 25 with primary 26 and secondary 2?, the secondary 21 being connected to the terminals of a resistance 2 8. One terminal of resistance 28 is connected to condenser 2|, whereas the other terminal leads to a mechanical interrupter with contact segments 3| separated by insulations 32, the segments being connected among themselves and to the second terminal of resistance 28 whereas a sliding contact 33 leads to condenser 2I and secondary I. Interrupter 3G is mechanically or otherwise driven in synchronism with generator 2, as indicated in the drawing by a common shaft 34 for 2 and 30. Generator and interrupter are so arranged that connection between resistance 28 and condenser 2| i's established only during a comparatively short period when the amplitude of the carrier wave supplied by 21S high. a

Any incoming signal waves determine a certain varying potential drop across resistance 28 which-supplies condenser 2! with a correspondingly varying potential, but only during the periods when the interrupter 3'8 establishes connection between resistance and condenser. Therefore the charge of condenser 2I during each period when it is connected to the signal input circuit-is determined by the potential drop across Wave in the output circuit of tube I0.

coupling resistance 28, which is proportionate to -the momentary amplitude of the incoming signal wave-1n other words, referring now again to Figs-l and 2, condenser 2! and coupling resistance 28 are connected during the transient period section E B, whereas during the sinusoidal period section B E, the signal inputcircuit is disconnected from the input circuit of tube Ell. Consequently, the average voltage across condenser 2|, and therefore across the input circuit of I8, is set at each transient period section according to the momentary value of the signal wave, and remains substantially constant during the remaining section B E of each cycle,

since-the only possible leakage path is through 'resi'sta-nce'il which can be dimensicned at such a high value that condenser 2I drains very slowly so that the section B E substantially retains its sinusoidal shape, and its amplitude is determined and set during the preceding transient. period E B.

The charge on condenser 21 therefore determines for each cycle of the signaled wave the mean potential -of-grid I5. This mean grid potential is shifted during each transient period section (provided the signal amplitude changes at all) proportionally to the momentary signal potential at that time across resistance '28, and

the carrier Wave is amplified accordingly. Fig. =4

shows how the shifting of the mean gr-id potenamplification is increased as shown by curves 53 and 52,-andw1th the grid potential at 44, the am- .plification is still higher. If the average amplitude of the signaled carrier is represented by curve 52, the signal wave may be utilized to shift the mean grid potential, and with it the amplitude of the signaled carrier in the output circuit, between two extremes represented by curves 5!! and54, without causing volume distortion, provided the corresponding section 4i! to 44 of the curve is parabolic and provided. that the. amplitude of the carrier wave 5|, 53, or 55 is low. This is 'due to the well known fact that the voltage amplification dependsupon the first derivative (or the steepness) of the curve, and the first derivative of a parabolic curve increases linearly. The working range of the curve, or the mean grid potential corresponding to point 42, can be set with the aid of variable grid voltage supply I'I. It will now be understood that, due to the influence of the momentary signalamplitude upon the carrier wave during thetransient section, which influence is substantially maintained during the ensuing sinusoidal section, the signaled carrier is composed of substantially sinusoidal and constant amplitude sections B E, connected by transientsect'ions B during which the amplitude is changed in accordance with the signal amplitude prevailing at that time. 7

Instead of employing to some extent mechanical means for producing a signaled carried according to the present invention,- a purely electrical arrangement according to Fig. 5 ca-n be used for the same purpose, especially in cases where the carrier frequency is high. Similar to the modification according to Fig. 3, an electron discharge device I00 with filament H4, grid I I5 and plate II6 has an output circuit battery HQ and in the control circuit a grid biasing battery I", a transformer secondary I01 and a high resistance H38 in series across the grid and fila ment terminals. Secondary I 61 is part of a transformer I05 whose primary IE6 is supplied with a'sinusoidal carrier Wave'of suitable con- 'sta-nt frequency. The signal waves are supplied to the primary! of a transformer I25, whose secondary 'IZT-is on the one side connected to 'plate I36 of a second electron discharge device 43]) and on'the other side through plate battery I29 and conductor I32 to thefilament I I4 of tube I00. The filament I34 of tube I 39 is connected to grid II5 of tube I09 by conductor I3 I and across conductors I 3| and I32 are a resistance I28 and a condenser I2I. An auxiliary transformer I 45' whose primary I46 is connected to a source of current having the same frequency, or a lower or higher harmonic thereof, as the carrier wave, supplies from its secondary l4! terminal I42 and tap I44 of a resistance I40, whose other terminal I43 is connected to 142 through a condenser I 49. A conductor I54 with two slide contacts I5I and I52 leads from a potentiometer I4I with battery I48 to resistance I40. Terminal I60 of the potentiometer is connected to conductor 132. A slidecontact I53 connects an adjustable point of resistance I40 to grid I35 of tube I30.

, CondenserIZI and resistances I28 and its in the control circuit of tube I function similar to the corresponding elements2l, 28, and 3 of Fig. 3, but the method of impressing during the transient period the momentary signal amplier phase relationandamplitude can be obtained by adjusting slide contacts I52 and I 53in a man ner which will be readily understood, one half of resistance I40 being connected directly across secondary WI whereas the other half is connected to the secondary in series with condenser I09. With the aid of potentiometer MI and battery I48, a biasing potential is applied to grid I35. The grid potential is so adjusted that the grid normally stops flow of current from plate I30 to filament I34, but permits it if its potential rises sufficiently over the biasing potential, when signal current is permitted to flow to resistance I28. Since the current applied to the grid from transformer I45 is in adjustable relationship to the carrier current supplied to transformer I05, the period of increased potential of grid I and therefore charge of resistance I28 by the signal current is adjustably controlled by the carrier wave; in other words, the momentary signal amplitude can be applied to resistance I28 during a transient period recurring. at certain predetermined intervals of the carrier wave, grid I35 operating as a trigger valve, which permits flow'of supplied by transformer I45 surpasses the biasing potential.

The placing of the transient period section within a carrier cycle depends upon the phase relationship of the carrier wave and the wave impressed upon grid I35. Presuming that the currents in I05 and I45 are in phase, this phase relationship can be changed with the aid of contacts I52 and I53 and condenser I49. In order to keep the average differential gradient or slope of the transient period section as far as possible close to that of the sinusoidal carrier wave, (which is important in order to avoid higher frequencies) attention must be given to the rate of charge and discharge ofcondenser IZI which infiuences the shape of the transient curve. Care.

is therefore necessary in selecting a tube I30 with proper'characteristics, suitable resistances I20 and I08 and a condenser IZI of corresponding dimensions. Although the relative characteristics of these elements permit many changes in accordance with prevailing conditions, I have found that for a carrier frequency of approximately 30,000 cycles a tube I30 of the 199 type,

having three elements, a resistance I28 of 10,000

ohms, a resistance I00 of 100,000 ohms, and a condenser I2I of .0003 m. f. Work satisfactorily.

If it is desired to have one transient period section per cycle, as shown in Figs. 1 and 2, the primary I00 and I46 can be supplied from the same source, which corresponds to one commutator segment per pole pair of the mechanical arrangement of Fig. 3. If it is, for example, desired to have a transient period section per half cycle, transformer Hi5 must be supplied with a frequency twice the carrier frequency. In other cases, where the signal frequency is low in comparison to the carrier frequency, it may be advantageous to have a transient period section only within every second, third or fourth cycle of the carrier wave, or even at greater intervals, in which case'transformer I45 must be supplied with a subharmonic of the carrier frequency, or impulses occurring at subharmonic intervals.

Since in a system according. to this invention only the frequency of the original sinusoidal carrier wave need be transmitted, the higher frequencies of low intensity which are due to the transient period may be filtered out, for example by a filter II!) of any suitable design in the output circuit of Fig. 5. In filtering and further amplifying the signaled carrier for transmission, it is essential that the decrement of the carrier frequency circuits is rather high, since otherwise the signaled carrier will tend to assumethe characteristics of an ordinary modulated carrier with itswide range of frequencies.

It will be understood that many variations of the arrangements of Figs. 3 and 5 are possible within the scope of this invention. For example, condensers 2i or I2I, respectively, may be replaced by an inductance coil for storing the charge intermediate the transient periods, or, in some cases, the filament battery I33 (Fig. 5) may have sufficient capacitance to replace condenser I2I. Also, electronic or gas discharge devices having two, four or more electrodes have characteristics suitable for operation in the place of electronic tube. I30.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. An electric signaling system comprising a source of substantially sinusoidal carrier current, an amplification circuit supplied from said source, means for changing the ratio of amplification of said current, during relatively brief predetermined period sections thereof, in accordance with a signal to be transmitted while otherwise maintaining the sinusoidal shape of said current, and means for operating said changing means in synchronism with said source.

2. An electric signaling system comprising an amplification circuit supplied from two sources of varying currents with different frequencies and regulating means controlled by both sources for adjusting the amplification of the. current supplied by one source in accordance with the configuration of the current supplied by the other source, during regularly recurring relatively brief period sections coordinated with the cycles of the current supplied by said first source.

3. Electric signaling apparatus comprising means 'for supplying substantially sinusoidal high frequency oscillations of substantially constant wave length and amplitude, means for supplying signal oscillations of comparatively low frequency, and means for combining said two oscillations during definite, uniform and comparatively short sections'within certain cycles of one of said oscillations.

4. Electric signaling apparatus comprising an amplification device, means for supplying high frequency oscillations and oscillations of comparatively low frequency to the input circuit of said device, and means for regulating the rate 70 of amplification of said high frequency oscillations in proportion to the momentary value of said low frequency oscillations, during period sections of less than a quarter cycle at intervals of multiples of a half cycle. 45

5. Electric signaling apparatus comprising an .electronic amplification device, means for applying high frequency voltages to the control electrode of'said device, and regulating means supplying a potential proportionate to the momenta-ry values of signal voltages to said control electrode during period sections at definite intervals in synchronism with said high frequency oscillations.

6. Electric signaling apparatus comprising an electronic amplification device, means for applying high frequency oscillations and signaling oscillations to the control electrode of said device, means for regulating the potential upon said electrode in accordance with the momentary values of said signaling oscillations during comparatively brief period sections at recurrent intervals synchronized with said high frequency oscillations, and means for substantially maintaining said potential intermediate said period sections.

7. Electric signaling apparatus comprising an electronic amplification device, means for supplyim high frequency oscillations to the input terminals of said device, means for applying a potential proportionate -to signal oscillations across said input terminals during comparatively brief period sections at definite intervals, and a reactance across said input terminals for substantially maintaining their potential during said intervals. 1

I 8. Apparatus for modulating the amplitude of a high frequency carrier wave in accordance with the configuration of a signaling wave, comprising an electronic amplifier supplied with said carrier wave, a contactor applying said signal wave to theinput terminals of said amplifier ,during definitelyspaced comparatively brief period sections in synchronism with saidcarrier wave, and a reactance across said terminals for substantially maintaining the input terminal potential intermediate said sections. V V

9. Electric signaling apparatus comprising an electronic amplification device, means for supplying a carrier current and a signaling current to the input terminals of said device, a reactance across said input terminals and electronic means for varying the potential across said reactance proportionate to the. value of said signaling current, during intermittent period sections recurrent in synchronism with said carrier current.

10. Electric high frequency signaling apparatus comprising means supplying a carrier current of substantially constant frequency, means supplying a signal current, means for amplifying said carrier current, means for regulating the amplification of said carrier current proportionally to the value of the signal current prevailing during certain recurrent carrier current period sections and means for substantially maintaining the amplification intermediate said period sections to the last amplification determined by said regulating means.

11. Electric signaling apparatus comprising an =tial. r

rupter for intermittently impressing a signal wave potential across said condenser and means for operating said interrupter in synchronism with said carrier Wave.

12. Electric signaling apparatus comprising an amplification tube, means including a high resistance for impressing "a carrier wave .potential upon the grid of said tube, a condenser across grid and filament. of said tube, a resistance parallel to said condenser, a control tube whose plate circuit includes in series said resistance and a source of signal potential, and means for'applying to the grid of said control tube acontrol potential in synchronism with 'said carrier poten- 13. The method of electric signaling which comprises producing a high frequency wave train and impressingsignals thereon by varying the amplitudes of consecutive substantially sinusoidal wave sections of said train in accordance with varying signal amplitudes during relatively brief periods of the high frequency wave, whereby transient sections connecting said sinusoidal ections of differing amplitudes are produced.

14. Electric signaling apparatus comprising means for supplying high frequency oscillations, and means for varying the amplitude of said high frequency oscillations in accordance with signals, said means beingisynchronized with said supply means for changing during relatively brief, and

uniformly recurrent sections of the high frequency oscillations the signal energy of saidoscillations, whereby brief transient sections connecting consecutive longer sections of'varying amplitudes but substantially sinusoidal wave form are produced. 7 V

' 15. The method of providing a modulated wave train, which comprises producing a train of substantially sinusoidal waves having substantially uniform amplitude, and impressing on said wave train signals by diversely varying the amplitudes of consecutive sinusoidal wave sections of said train' during comparatively short periods of the Wave train, whereby transient sections connecting said sinusoidal wave sections in accordance with the varying amplitudes of a modulating signal are produced.

16. The method of electric signaling which comprises producing a high frequency wave train and impressing on said train signals by varying the amplitudes of consecutivesubstantially sinusoidal wave sections of said train in accordance with the varying amplitudes of a signal, during periods of the high frequency wave train of less than a quarter cycle and at phase intervals of multiples of a half cycle of said train whereby transient sections connecting said sinusoidal sections of different amplitudes are produced.

j AUSTIN GICOOLEY. 

